Lara Croft and the Guardian of the Light goes free on Square's Core Online service
Lara Croft and the Spear of Infinite Spearing would be a better name for this top-down Tomb Raider, which has won me over in the last half-hour by being both good and also sort-of free. RPS note that it's available to play in Chrome now through the Core site, which lets you watch ad to earn game time. Six minutes in, the game minimizes and a box pops up offering a choice of advertisements, each worth a different number of minutes.
I watched a one minute advert for Mini Ninjas and got 24 minutes of play, which seems like a reasonable deal if you're just looking to try it out. If you can't stand those sudden interruptions, you can play the ad-free version for $10. If you're not interested in this browser-based malarky a demo is also available through Steam.